Aqua regia reactions with

Sometimes, solids are so insoluble that combinations of reactions are needed to dissolve them. For example, to dissolve the extremely insoluble HgS (Ksp = 1.6 X 10 54), we must use a mixture of concentrated HC1 and concentrated HN03, called aqua regia. The H+ ions in the aqua regia react with the S2- ions to form H2S, and Cl- reacts with Hg2+ to form various complex ions such as HgCLt2-. In addition, N03 oxidizes S2 to elemental sulfur. These processes lower the concentrations of Hg2+ and S2 and thus promote the solubility of HgS. 

At the end of the 17 century interest arose in the difference between the natural products soda, sodium carbonate on one side and potash, potassium carbonate on the other. The former was called mineral alkali, the latter vegetable alkali. It was early established that there is a relationship between sea salt and soda and between saltpeter (potassium nitrate) and potash. Johaim Bohn in Leipzig made one of the first systematic observations in 1683. He distilled nitric acid with sea salt present, to prepare aqua regia. Crystals with an obvious cubic structure were deposited in the retort (he called it cubic saltpeter it was probably cubic sodium chloride). From the reaction between nitric acid and potash, without sea-salt present, he got beautiful crystals of quite a different form (presumably saltpeter, potassium nitrate, which crystaUizes in the orthorhombic system in prismatic crystals). 

Titanium carbide is resistant to aqueous alkaU except in the presence of oxidising agents. It is resistant to acids except nitric acid, aqua regia, and mixtures of nitric acid with sulfuric or hydrofluoric acid. In oxygen at 450°C, a nonprotecting anatase coating forms. The reaction... 

Aminoglycoside antibiotics and / -substituted indoles are stained red. Pyrrole derivatives with free / -positions react at room temperature to yield blue-colored zones [11]. Exposure to the vapors of aqua regia deepens the colors. This reaction sometimes produces fluorescence [3]. The detection limit for monomethylhydrazine is 200 pg per chromatogram zone [3]. 

Write a balanced redox equation for the reaction of mercury with aqua regia, assuming the products include HgCl/ and N02(g). 

Velocity Most metals and alloys are protected from corrosion, not by nobility [a metal s inherent resistance to enter into an electrochemical reaction with that environment, e.g., the (intrinsic) inertness of gold to (almost) everything but aqua regia], but by the formation of a protective film on the surface. In the examples of film-forming protective cases, the film has similar, but more limiting, specific assignment of that exemplaiy-type resistance to the exposed environment (not nearly so broad-based as noted in the case of gold). Velocity-accelerated corrosion is the accelerated or increased rate of deterioration or attack on a metal surface because of relative movement between a corrosive fluid and the metal surface, i.e., the instability (velocity sensitivity) of that protective film. 

Evolution of phosphine is slow in contact with water or alkali, but explosively violent in contact with dilute mineral acids [1], However, reports of violent interaction with concentrated or dilute hydrochloric acid, and of explosive reaction with 1 1 aqua regia, have been questioned [2],... 

Elemental composition Ni 53.00%, C 21.69%, N 25.30%. The compound may be identified by x-ray and selective chemical reactions with cyanide ions. Nickel may be analyzed in an acidified aqueous solution after it is solubilized with concentrated nitric acid or aqua regia (See Nickel). 

Tin is attacked by concentrated acids. With dilute acids the reaction may be slow or very slow. The metal readily reacts with hot concentrated hydrochloric acid and aqua regia but slowly with cold dilute hydrochloric acid. The reaction also is slow with hot dilute sulfuric acid, which dissolves the... 

Hydrochloro-Auric Acid. Treat gold with aqua regia. When the metal dissolves, add 1 ml of concentrated hydrochloric acid and evaporate the solution until crystals appear. What is the composition of the obtained substance Dissolve several crystals of the compound in water, add to one half of the solution several drops of a soluble cesium salt, and to the other half a 0.1 N potassium hydroxide solution. What forms Write the equations of the reactions. 

There are, however, certain chemical reactions by which platinum may be readily distinguished and separated from the gold in solution. Sulphate of iron and oxalic acid, which precipitate gold, do not precipitate platinum. When the latter is dissolved in aqua regia, and the acid neutralized by carbonate of soda, it is deposited as a black powder, if the mixture be boiled with tartaric acid and sodar—the ingredients of a Seid-litz powder. Further, the addition of chloride of ammonium and alcohol te a strong solution of platinum, causes the deposition of a yellow crystalline precipitate, which is charactsristtc of this metal. These and other reactions may be summarily stated as follows... 

Application of the Jkagmts,—Having thus described the properties and characteristic reactions of the different metals which it is desirable to look for as being frequently associated with gold, lot it now be assumed that the substance to be examined is a piece of. auriferous quartz, TbiB must be first reduced to powder, and then boiled for some time in an earthenware or glass dish with aqua regia. The solution ie then diluted with water, passed through a filter, and allowed to cool. If any silver bo present, it will remain in the filter as a white precipitate, mixed with the quartz. 

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